(a)
balanced reaction :
FeCl3•7H2O + 3 HCO3-     Â
--------------------------> Fe(OH)3(s) + CO2 + 3 Cl- + 7H2O
b)
FeCl3•7H2O + 3 HCO3-     Â
--------------------------> Fe(OH)3(s) + CO2 + 3 Cl- + 7H2O
288.3
g                                                                    Â
106.87 g
20 x 10^-3
g                                                               Â
?
Fe(OH)3 mass = 20 x 10^-3 x 106.87 / 288.3
                        Â
= 7.41 x 10^-3 g
                       Â
= 7.41 mg /L
ferric hydorxide = 7.41 mg /L